A planar thin display device used in an electronic device usually includes a display panel having a display surface on which an image is displayed, a driving component (such as an integrated circuit driver) for displaying an image, and a backlight that applies light to the rear surface of the display panel.
Known types of backlights include a direct-lit backlight in which the light sources are disposed on the rear side of the display panel and an edge-lit backlight (or a side-lit backlight) in which the light sources face the end surface of the light guide plate such that the backlight emits planar light. The edge-lit backlight is superior in terms of thickness reduction capability. However, in the edge-lit backlight, LEDs (light emitting diodes), which are the light sources, are concentrated in a local area. The LEDs may be excessively heated when the backlight is in continuous operation over a long time period, making the lighting state of the LEDs unstable or causing the light guide plate to deform. This may result in uneven luminance or uneven brightness, for example, leading to a decrease in the display quality of the display panel.
To solve the problem, a technique for heat dissipation has been developed to suppress an increase in temperature of the LEDs and portions around the LEDs. For example, Japanese Patent No. 5635322 discloses a liquid crystal display device including a graphite composite film having high heat conductivity. The graphite composite film is attached to an outer surface of a frame that has a light-emitting module including LEDs on an inner surface thereof. The neat from the LEDs is dissipated through the frame.
A COG (Chip On Glass) display device in which a driving component for displaying an image is directly mounted on a periphery of a substrate of the display panel is widely employed in electronic devices that have been demanded to have a smaller size and a lighter weight, such as tablet computers, digital cameras, and smart phones.
The driving component generates heat when driven. If the heat is not sufficiently dissipated, the service life of the driving component would be shortened, or the driving reliability would be lowered. Furthermore, in the display device including the driving component that is mounted on the substrate of the liquid crystal panel by COG technology, the liquid crystal panel may be heated to a temperature above the liquid crystal transition temperature by the heat. In such a case, the display quality of the image is lowered. Furthermore, if a finger print sensor or the like is disposed around the driving component, the heated driving component may cause low temperature burn or malfunction, for example.
In recent years, the driving component generates more heat as the number of LEDs and a load on the driving component increase due to an increase in the resolution of the display image and the faster driving speed of the driving component. Furthermore, as the electronic devices are widely used, higher heat dissipation performance is required to enable the display device to properly operate under various circumstances. In particular, a display device including components, such as a cover glass and a touch panel, on a front side of the display panel is more likely to have the above-described problem, because a space between the components is small and heat is likely to stay in the space. Under such a circumstance, the heat dissipation performance of the display device is demanded to be further improved.